5.5 month old - night wakes

My 5.5 month wakes every hour/40 minutes for the last 1 month. Used to do 7-hour stretches earlier but now

I’m exhausted and sometimes co-sleep, but he feeds/moves nonstop so I still get no rest.

Day naps (2.5 - 3.5 hours) and wake windows(1.75/2/2/2.5) are good.

He sleeps late around 9:30 to 10pm which I am shifting to earlier bed time.

Room temp is 18–20°C - use sleep suit + 2.5 tog.

He settles himself for naps/half of bedtimes. Night wakeups are a different story - he needs nursing or being walked back to sleep. Tried pain relief in case it’s teething, no change.

Any advice? Affordable sleep consultant or book recommendations also welcome!”